JP5260977B2 - Method for producing fiber-reinforced composite material and fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material whose cured resin includes a carbon fiber, the fiber-reinforced composite material being excellent in surface smoothness. <P>SOLUTION: The process of making a fiber-reinforced composite material has a step of applying to a preopened carbon fiber a sizing agent with a mass average molecular weight of 1,000-10,000 so as to be contained in 3-10 mass%, a step of obtaining a prepreg by impregnating a curable resin to the carbon fiber to which the sizing agent has been applied, and a step of curing the prepreg. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a fiber reinforced composite material containing carbon fibers in a cured resin and a fiber reinforced composite material.

Conventionally, a method for producing a fiber reinforced composite material containing glass fibers in a cured resin, which is capable of obtaining a molded article having excellent surface smoothness, and forming a gel coat layer on the surface of the fiber reinforced composite material Has been proposed (see, for example, Patent Document 1). In this method for producing a fiber-reinforced composite material, a resin composition containing a fluoropolymer and a curing agent is applied to a mold and backed with a mat made of glass fibers, and then the resin composition is cured.
In this manufacturing method, the surface smoothness of the fiber reinforced composite material is improved by forming the gel coat layer on the surface of the fiber reinforced composite material.
Such fiber reinforced composite materials are used as outer plates for automobile fenders, doors, trunks and the like because of their high strength and elastic modulus.

However, in the fiber reinforced composite material containing the conventional glass fiber, since the density of the glass fiber is high, the specific strength and the specific elastic modulus remain at the same level as the metal material. Therefore, if a fiber reinforced composite material containing carbon fiber, which has a lower density than glass fiber, can be used for the outer panel of an automobile, the weight of the vehicle body can be reduced, improving fuel efficiency, reducing emissions, and improving handling. Can be achieved.
JP-A-2-173128

However, the conventional fiber-reinforced composite material containing carbon fiber in the cured resin has insufficient surface smoothness. More specifically, even if the carbon fibers included in the resin are pre-opened, if the flow distance of the material during molding is long, uniform dispersion of the carbon fibers may be hindered. If the dispersion of the carbon fibers is inhibited, the fiber-reinforced composite material is sinked at the resin-rich portion, and the surface smoothness is impaired.
Further, the surface smoothness of the fiber reinforced composite material is impaired by the flow of the material at the time of molding, and the carbon fibers undulate in the thickness direction of the fiber reinforced composite material.

  Then, the subject of this invention is a fiber reinforced composite material which contains carbon fiber in the hardened resin, Comprising: It is providing the fiber reinforced composite material excellent in surface smoothness.

In the method for producing a fiber-reinforced composite material of the present invention that solves the above problems, a sizing agent having a mass average molecular weight of 1000 to 10000 is applied to carbon fibers that have been opened beforehand so that the content is 3 to 10% by mass. A step of obtaining a prepreg by adding a curable resin to the carbon fiber coated with the sizing agent, and clamping the prepreg in a predetermined mold, and by the flow of the curable resin at the time of clamping And a step of separating and curing the carbon fiber .
Moreover, in such a manufacturing method, it is desirable that the sizing agent is an epoxy resin or a vinyl ester resin.
And the fiber reinforced composite material of the present invention that solves the above problems is a carbon fiber obtained by applying a sizing agent having a mass average molecular weight of 1000 to 10000 to 3 to 10% by mass on a previously opened carbon fiber, A prepreg containing a curable resin is clamped in a predetermined mold, and the carbon fibers are separated and cured by the flow of the curable resin during the mold clamping .

  ADVANTAGE OF THE INVENTION According to this invention, it is a fiber reinforced composite material which contains carbon fiber in the hardened resin, Comprising: The fiber reinforced composite material excellent in surface smoothness can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the drawings referred to here, FIG. 1 is a process explanatory diagram of a method for manufacturing a fiber-reinforced composite material according to an embodiment.
The fiber-reinforced composite material obtained by the production method according to the present invention is obtained by applying a sizing agent having a mass average molecular weight of 1000 to 10000 to a carbon fiber that has been opened beforehand so that the content is 3 to 10% by mass. Main features. Below, the fiber reinforced composite material obtained by this manufacturing method is demonstrated, explaining the manufacturing method which concerns on this invention.

  As shown in FIG. 1, the method for producing a fiber-reinforced composite material according to the present embodiment includes a fiber-opening step for opening carbon fibers, a sizing agent application step for applying a sizing agent to the opened carbon fibers, There are a prepreg manufacturing process for obtaining a prepreg by adding a curable resin to a carbon fiber coated with a sizing agent, a laminating process for laminating the prepreg, and a molding process for clamping and curing the prepreg in a predetermined mold. doing.

Examples of the carbon fiber used in the opening process described above include polyacrylonitrile-based carbon fiber, rayon-based carbon fiber, and pitch-based carbon fiber. The carbon fiber in this embodiment is formed by bundling about 1000 to 24000 filaments.
In this opening process, the width of the carbon fiber is widened and the thickness of the carbon fiber is reduced. Examples of the method for opening the carbon fiber include a method of blowing air to the carbon fiber. For this opening, a known air opening device (for example, see JP-A-11-172562) may be used.

The sizing agent used in the above-described sizing agent coating step is preferably made of a component insoluble in a monomer (for example, styrene monomer) contained in the curable resin described later, and its surface energy is the surface energy of the curable resin. It is desirable to be close. Further, the sizing agent needs to be able to maintain the carbon fiber convergence form from the impregnation of the curable resin to the molding flow. Specifically, those having an epoxy resin or vinyl ester resin as a main component are desirable.
Such a sizing agent prevents the carbon fibers from softening and makes it easier to loosen the carbon fibers in the curable resin at the time of mold clamping, as compared with those soluble in the curable resin monomer.
Examples of the epoxy resin include bisphenol A type epoxy resins. As the epoxy resin, commercially available products can be suitably used. Examples of commercially available products include EP1001 manufactured by Japan Epoxy Resin, EPICLON 840 manufactured by DIC, and Adeka Resin EP4500 manufactured by ADEKA.
Examples of the vinyl ester resin include epoxy acrylate resins having an acrylic group or a methacryl group in one molecule, and include bisphenol A type vinyl ester resins, novolac type vinyl ester resins, brominated vinyl ester resins and the like.
Further, the sizing agent in this embodiment may be a urethane-modified resin such as an epoxy resin or a vinyl ester resin as described above.
And the mass mean molecular weight of such a sizing agent is 1000-10000. In addition, the sizing agent having a mass average molecular weight of 1000 or more can effectively separate the carbon fiber with the clamping pressure in the clamping process, as will be described later. Moreover, the sizing agent having a mass average molecular weight of 10,000 or less can suppress the carbon fiber in the resin from becoming rigid in the prepreg manufacturing process described later.

The sizing agent applied to the opened carbon fiber is preferably a water-soluble emulsion. When such a sizing agent is applied to the carbon fiber, its concentration control is easy and control of a predetermined application amount described later can be facilitated, and an organic solvent is not used, so the environmental load is reduced. Can do.
Although there is no restriction | limiting in particular as a method of apply | coating such a sizing agent to the opened carbon fiber, A dipping method is desirable. Specifically, a method of winding the carbon fiber and winding it from the reel side to the winding reel side through a tank in which the sizing agent is stored can be mentioned.
The coating amount of the sizing agent is 3 to 10% by mass, preferably 5 to 10% by mass, based on the content of the sizing agent in the carbon fiber after the sizing agent is applied and dried.

In the above-described prepreg production step, a plurality of carbon fibers are cut into an appropriate length, and a prepreg is produced by including a curable resin therein. The length of the carbon fiber to be cut is preferably about 12 mm to 50 mm. Thus, by setting the length of the carbon fiber to 12 mm or more, the molded product (fiber reinforced composite material) can sufficiently exhibit mechanical properties such as tensile strength. By making the length of the carbon fiber 50 mm or less, the carbon fiber can be more surely and uniformly dispersed in the curable resin, and the resulting molded product (fiber reinforced composite material) has a good surface smoothness. Sex can be imparted.
Examples of the curable resin include thermosetting resins such as epoxy resins, vinyl ester resins, unsaturated polyester resins, and urethane resins.
Incidentally, when preparing the prepreg, the carbon fiber may contain a filler, a thermoplastic resin, other additives, etc. in addition to the above-described thermosetting resin, as long as the problems of the present invention are not impaired. it can.

A plurality of the prepregs thus produced are laminated in the above-described lamination process, and are clamped and cured in the molding process. At this time, a curable resin may be further added into the mold.
The mold clamping pressure is a pressure at which the carbon fibers are more effectively separated, and is preferably 5 MPa or more.

  Here, “dividing the carbon fiber” will be described with reference to FIGS. 2 (a) and 2 (b). FIG. 2A is a drawing-substituting photograph showing the state of the carbon fiber that has been divided. FIG. 2B is a drawing-substituting photograph showing, as a comparative example, a state in which a carbon fiber that has not been separated is formed with a resin-rich portion in accordance with the resin flow in the molding process.

  As shown in FIG. 2 (a), the separation of the carbon fiber 1 is to divide the carbon fiber 1 into a plurality of bundles of filaments 1a in the curable resin 2 so as to form a fan-shaped (shark fin) shape. It means that the interval between the plurality of filament bundles 1a becomes wider as the end of the carbon fiber 1 becomes closer. Such splitting of the carbon fiber 1 occurs when the sizing agent having the above-described predetermined mass average molecular weight is contained in the carbon fiber at a content of 3 to 10% by mass.

  On the other hand, as shown in FIG. 2 (b), the carbon fiber shown as a comparative example that has not been fiber-divided maintains the width of the opened carbon fiber 1 after being clamped. And, for example, in the curable resin 2, the overlapping carbon fibers 1 are in the mold with the flow of the curable resin 2 while restraining each other so as to maintain the width of the opened carbon fiber 1. Moving. As a result, the curable resin is unevenly distributed in the clamped prepreg to form the resin rich portion 3.

  The fiber-reinforced composite material according to the present embodiment including carbon fibers is obtained by curing the prepreg in the mold in the molding step described above. The prepreg may be cured according to the type of curable resin to be used. For example, the prepreg containing the thermosetting resin may be heat-cured under a predetermined pressure with a press machine using a temperature control die.

Next, functions and effects of the fiber-reinforced composite material and the manufacturing method thereof according to the present embodiment will be described.
In the manufacturing method according to the present embodiment, the above-described sizing agent is applied to the carbon fiber that has been previously opened in the above-described predetermined amount, so that the carbon fiber is aligned in the thickness direction of the prepreg by resin flow during mold clamping. It is prevented from bending in a undulating manner. And since the carbon fiber is prevented from swelling due to the resin flow at the time of mold clamping and its linearity is secured, the formation of the resin rich portion that causes the resin sink near the surface of the prepreg is suppressed.
As a result, the fiber-reinforced composite material obtained by this manufacturing method is prevented from forming the resin-rich portion that causes the resin sink while preventing the bending of the carbon fiber as described above. Excellent smoothness.

Moreover, in the conventional manufacturing method of the fiber reinforced composite material containing carbon fiber, as mentioned above, the mold was clamped so that the filament of carbon fiber spreads in the mold while maintaining the interval by the resin flow at the time of mold clamping. A resin rich portion is formed in the prepreg. In particular, in the portion where the carbon fibers overlap each other in the thickness direction (stacking direction) of the prepreg, the tendency that the interval between the filaments is constrained becomes significant.
On the other hand, in the manufacturing method according to the present embodiment, the sizing agent described above is applied to the carbon fiber (filament bundle) that has been previously opened in the predetermined amount, so that the resin flow during clamping With this, the carbon fiber is separated. That is, the interval between the carbon fibers becomes wider as the carbon fiber filaments are closer to the end of the carbon fibers. As a result, in the manufacturing method according to the present embodiment, the resin-rich portion is more effectively suppressed from being formed in the clamped prepreg as compared with the conventional manufacturing method. Therefore, the fiber reinforced composite material obtained by the manufacturing method according to the present embodiment has excellent surface smoothness.

  In addition, as described above, the fiber-reinforced composite material obtained by the manufacturing method according to the present embodiment includes carbon fibers having a lower density than glass fibers while having excellent surface smoothness. It is lighter than a fiber reinforced composite material containing glass fibers.

  As described above, according to the fiber-reinforced composite material and the manufacturing method thereof according to the present embodiment, by setting the composition, molecular weight, and coating amount of the sizing agent applied to the previously opened carbon fiber as described above. The surface smoothness can be made excellent while reducing the weight of the obtained fiber-reinforced composite material.

Next, the present invention will be described more specifically with reference to examples.
(Example 1 to Example 3)
In Example 1 to Example 3, a fiber-reinforced composite material using polyacrylonitrile-based carbon fiber (manufactured by Toho Tenax Co., Ltd., HTA-12K-E30, convergence width 6 mm, convergence thickness 0.15 mm) as a carbon fiber is manufactured. did. This carbon fiber was previously opened. Incidentally, the fiber opening was performed using a fiber opening device according to the fiber opening device described in JP-A-11-172562. The width of the carbon fiber after opening was 16 mm, and the thickness was 0.06 mm.

Next, a sizing agent was applied to the opened carbon fiber. As the sizing agent, a bisphenol A type epoxy resin (manufactured by HEXION, water-soluble epoxy resin Epiletz (registered trademark) 3540WY-55 (mass average molecular weight 2000)) was used.
The sizing agent is applied by feeding the carbon fiber from the reel side to the take-up reel side through the opening device and the tank storing the water-soluble emulsion of the sizing agent. It was.
In each of Examples 1 to 3, the application amount of the sizing agent was set as shown in Table 1. This coating amount is the content (% by mass) of the sizing agent in the carbon fiber (hereinafter sometimes simply referred to as “carbon fiber containing the sizing agent”) after the water-soluble emulsion of the sizing agent is applied and dried. ).

  Next, the bending load of the carbon fiber containing the sizing agent was measured. The bending load was measured as shown in FIG. FIG. 3 referred to here is a conceptual diagram showing how the bending load of the carbon fiber containing the sizing agent is measured. In addition, the measurement piece of the carbon fiber (16 mm in width) containing the sizing agent used in this measurement was cut to a length of 30 mm.

  As shown in FIG. 3, the measurement of the bending load using this measurement piece 10 was performed about what was cantilevered by the jig | tool 11 which clamps the edge part of the measurement piece 10 by the length of 10 mm. In this measurement, the weight 12 is placed on the tip of the measuring piece 10 extending from the jig 11 with a length of 20 mm, and the weight 12 is slid down from the measuring piece 10 bent according to the weight of the weight 12. Was determined as a bending load (g). The results are shown in Table 1 and FIG. Here, FIG. 4 is a graph showing the relationship between the application amount of the sizing agent and the bending load of the carbon fiber containing the sizing agent. The vertical axis shows the bending load (g) of the carbon fiber, and the horizontal axis shows the carbon fiber. The coating amount (mass%) of the sizing agent is shown.

  Next, a carbon fiber containing a sizing agent obtained in each of Examples 1 to 3 was impregnated with a resin solution to prepare a prepreg. The resin liquid was prepared by mixing 100 parts by weight of unsaturated polyester (thermosetting resin), 120 parts by weight of calcium carbonate, and 6 parts by weight of vinyl acetate elastomer. The impregnation of the resin liquid into the carbon fiber was performed by supplying the carbon fiber to the SMC impregnation machine manufactured by Tsukishima Kikai Co., Ltd. at a speed of 5 m / min. In addition, the state of the carbon fiber supplied to this impregnation machine was visually evaluated according to the judgment criteria described below. The results are shown in Table 1.

  The condition of the above-mentioned carbon fiber was evaluated as good when no fluff was evaluated and marked as “◯” in Table 1, and when fluff was evaluated as bad, it was marked as “Δ” in Table 1 and markedly fluffed. In Table 1, “×” was evaluated as the worst and the case in which the occurrence of rupture occurred (the filament breakage was remarkable) was evaluated as the worst.

  Next, the obtained prepreg was set to a size of 100 mm × 150 mm × 20 mm so as to be 20% of the mold area. Incidentally, as the mold, a pseudo mold having a curved surface whose surface is curved with a predetermined curvature and simulating the outer plate of an automobile was used. Then, using a press machine (200t) manufactured by Kawasaki Oil Works Co., Ltd., the prepreg was pressurized and cured so that the clamping pressure was 10 MPa, to obtain a fiber-reinforced composite material. The mold clamping time at this time was 4 minutes, and the mold temperature for curing the prepreg was set to 140 ° C.

About the obtained fiber reinforced composite material, the volume fraction (Vf:%) and density (g / cm ³ ) of carbon fibers in the fiber reinforced composite material are measured, and the cross section of the fiber reinforced composite material is visually observed. The state of carbon fiber and the impregnation state of the curable resin were observed and evaluated according to the criteria described below. The results are shown in Table 1. In addition, the density measuring machine (SD-120L) made from MIRGE was used for the measurement of density (g / cm < ³ >).

  The above-described carbon fiber state of the fiber reinforced composite material is evaluated as good when the carbon fiber is not curved and is marked as “◯” in Table 1, and when the carbon fiber is curved as bad. “X” is shown in Table 1.

  The impregnation state of the curable resin of the fiber reinforced composite material is evaluated as good when the curable resin is sufficiently impregnated between the carbon fibers and is marked as “◯” in Table 1, and between the carbon fibers. In Table 1, “x” was evaluated as bad if the surface of the fiber-reinforced composite material was not sufficiently impregnated with the curable resin and the surface of the fiber-reinforced composite material was uneven due to the swelling caused by the voids.

(Comparative Example 1)
In Comparative Example 1, except that the amount of calcium carbonate in the resin liquid impregnated in the carbon fiber containing the sizing agent was 180 parts by mass instead of 120 parts by mass in “Example 1 to Example 3,” Carbon fibers containing a sizing agent were produced in the same manner as in “Example 1 to Example 3”, and fiber reinforced composite materials were obtained using the carbon fibers. Table 1 shows the application amount of the sizing agent.

And the bending load of the carbon fiber containing a sizing agent, the volume fraction (Vf:%) of the carbon fiber in the fiber-reinforced composite material, and the density (g / cm ³ ) are the same as those in “Example 1 to Example 3”. The state of the carbon fibers supplied to the impregnation machine, the state of the carbon fibers of the fiber reinforced composite material, and the state of impregnation of the curable resin of the fiber reinforced composite material are “Example 1 to Example 3”. Evaluation was made based on the same criteria. The results are shown in Table 1, and the measurement results of the bending load of the carbon fiber containing the sizing agent are also shown in FIG.

(Comparative Example 2 and Comparative Example 3)
In Comparative Example 2 and Comparative Example 3, except that the application amount of the sizing agent was changed as shown in Table 1, carbon fibers containing the sizing agent were produced in the same manner as in "Example 1 to Example 3," This carbon fiber was used to obtain a fiber reinforced composite material.

And the bending load of the carbon fiber containing a sizing agent, the volume fraction (Vf:%) of the carbon fiber in the fiber-reinforced composite material, and the density (g / cm ³ ) are the same as those in “Example 1 to Example 3”. The state of the carbon fibers supplied to the impregnation machine, the state of the carbon fibers of the fiber reinforced composite material, and the state of impregnation of the curable resin of the fiber reinforced composite material are “Example 1 to Example 3”. Evaluation was made based on the same criteria. The results are shown in Table 1, and the measurement results of the bending load of the carbon fiber containing the sizing agent are also shown in FIG.

(Evaluation of fiber reinforced composite materials in Examples 1 to 3 and Comparative Examples 2 to 3)
As shown in Table 1, the fiber-reinforced composite materials (Example 1 to Example 3) prepared using carbon fibers having a sizing agent coating amount of 3% by mass to 10% by mass have a carbon fiber curvature. In addition, the impregnation state of the curable resin was also good. In addition, no fuzz was observed in the carbon fiber delivered to the impregnation machine for producing the prepreg. On the other hand, fuzz was recognized in the carbon fiber (Comparative Example 1 and Comparative Example 2) in which the application amount of the sizing agent was less than 3 mass%. And the fiber reinforced composite material (Comparative Example 1) produced using the carbon fiber with the least amount of application | coating of a sizing agent had the carbon fiber curved.
In addition, the fiber reinforced composite material (Comparative Example 3) produced using carbon fibers in which the coating amount of the sizing agent exceeds 10% by mass is insufficient for impregnation of the curable resin into the carbon fibers. Unevenness occurred on the surface of the reinforced composite material.

  And as shown in FIG. The fiber-reinforced composite materials (Example 2 and Example 3) produced using carbon fibers having a sizing agent coating amount of 5% by mass or more have a bending load of the carbon fiber exceeding 5 g and the sizing agent coating. It has been found that the bending load of the carbon fiber remains flat even when the amount exceeds 10% by mass. That is, as described above, in consideration of the occurrence of irregularities on the surface of the fiber reinforced composite material (Comparative Example 3) using carbon fibers having a coating amount of 15 mass%, the application amount of the sizing agent is 3 It has been confirmed that a fiber reinforced composite material using carbon fibers of 10% by mass to 10% by mass, preferably 5% by mass to 10% by mass is preferable.

(Examples 4 to 11 and Comparative Examples 4 to 6)
In Examples and Comparative Examples herein, “Example 1 to Example 3” except that the sizing agent having the mass average molecular weight shown in Table 2 was used and the coating amount of the sizing agent was set as shown in Table 2. In the same manner as above, a carbon fiber containing a sizing agent was produced, and a fiber-reinforced composite material simulating an automobile outer plate was obtained using the carbon fiber.

  In addition, the convergence agents of Examples 4 to 11 and Comparative Examples 4 to 6 were selected from EPICLON (liquid epoxy resin) manufactured by DIC and those having a mass average molecular weight shown in Table 2.

  And about the obtained fiber reinforced composite material, while measuring the volume fraction (Vf:%) of carbon fiber in a fiber reinforced composite material, surface roughness Ra (micrometer), and surface waviness (micrometer), The condition of the surface of the fiber reinforced composite material was evaluated according to the criteria described below. The results are shown in Table 2. A surface roughness measuring machine (SV3000CNC) manufactured by Mitutoyo Corporation was used for measuring the surface roughness Ra (μm). The surface waviness (μm) was determined as the difference (absolute value) between the maximum height and the minimum height of the irregularities measured on the surface of the obtained fiber-reinforced composite material over a straight line of 30 mm.

  The above-mentioned surface state of the fiber reinforced composite material is evaluated as good when the irregularities are not visually recognized as “◯” and described in Table 2, and when the irregularities are visually observed as bad. X "and described in Table 2.

  And the uneven | corrugated height of the surface of the fiber reinforced composite material obtained in each of Example 5 and Comparative Example 4 was measured, and it graphed. This unevenness height was measured over 30 mm in a straight line at approximately the center of the surface of the fiber-reinforced composite material. FIG. 5A is a graph showing the uneven height on the surface of the fiber-reinforced composite material obtained in Example 5, and FIG. 5B is the surface of the fiber-reinforced composite material obtained in Comparative Example 4. It is a graph which shows the uneven | corrugated height in. The vertical axis represents the uneven height (μm), and the horizontal axis represents the measurement length (mm). In addition, the uneven | corrugated height (micrometer) of a vertical axis | shaft was shown with the relative value on the basis of the height of a measurement start position (0 micrometer). And the uneven | corrugated height of the metal mold | die corresponding to these measurement positions was written together with the broken line.

(Evaluation of fiber reinforced composite materials in Examples 4 to 11 and Comparative Examples 4 to 6)
As shown in Table 2, the fiber reinforced composite material (Example 4 to Example 11) using carbon fibers containing a sizing agent having a mass average molecular weight of 1000 or more and 10,000 or less has a good surface condition and unevenness. It was not recognized, and it was confirmed that the surface roughness Ra and the surface waviness were small.

In contrast, a fiber reinforced composite material using a carbon fiber containing a sizing agent having a mass average molecular weight of less than 1000 (Comparative Example 4), and a fiber reinforced using a carbon fiber containing a sizing agent having a mass average molecular weight exceeding 10,000. The composite materials (Comparative Example 5 and Comparative Example 6) had large surface waviness, and irregularities were observed on the surface by visual observation. In particular, in Comparative Example 4 and Comparative Example 6, even if the application amount of the sizing agent is within the above-described range (5% by mass), if the mass average molecular weight of the sizing agent is out of the range of 1000 to 10,000, It was confirmed that irregularities were formed on the surface of the reinforced composite material.
And it was confirmed that the fiber reinforced composite material (Example 4 to Example 11) using the carbon fiber containing the sizing agent having a mass average molecular weight of 1000 or more and 10,000 or less is excellent in surface smoothness.
Moreover, as shown to Fig.5 (a), the uneven | corrugated height of the surface of the fiber reinforced composite material obtained in Example 5 was substantially the same as the corresponding uneven | corrugated height in a metal mold | die.
On the other hand, the surface of the fiber-reinforced composite material obtained in Comparative Example 4 was formed with a dent that was thought to have formed sink marks at the resin-rich portion, as shown in FIG.
From the above, it was confirmed that the surface smoothness of the fiber-reinforced composite material according to the example is superior to the surface smoothness of the fiber-reinforced composite material according to the comparative example.

It is process explanatory drawing of the manufacturing method of the fiber reinforced composite material which concerns on embodiment. (A) is a drawing-substituting photograph showing a state of a carbon fiber that has been divided. (B) is a drawing-substituting photograph showing, as a comparative example, a state in which a carbon fiber that has not been divided is formed with a resin-rich portion in accordance with the resin flow in the mold clamping step. It is a conceptual diagram which shows a mode that the bending load of carbon fiber containing a sizing agent is measured. It is a graph which shows the relationship between the application amount of a sizing agent, and the bending load of the carbon fiber containing a sizing agent, a vertical axis | shaft shows the bending load (g) of carbon fiber, and a horizontal axis shows the application amount of the sizing agent contained in carbon fiber. (Mass%) is shown. (A) is a graph which shows the uneven | corrugated height in the surface of the fiber reinforced composite material obtained in Example 5, (b) is uneven | corrugated height in the surface of the fiber reinforced composite material obtained in Comparative Example 4. It is a graph which shows.

Explanation of symbols

10 Measurement piece (fiber reinforced composite material)
11 Jig

Claims (3)

A step of applying a sizing agent having a mass average molecular weight of 1000 to 10000 to a carbon fiber that has been opened in advance so that the content is 3 to 10% by mass;
Including a curable resin in the carbon fiber coated with the sizing agent to obtain a prepreg;
A step of clamping the prepreg in a predetermined mold, and separating and curing the carbon fibers by the flow of the curable resin at the time of clamping ;
A method for producing a fiber-reinforced composite material, comprising:   The method for producing a fiber-reinforced composite material according to claim 1, wherein the sizing agent is an epoxy resin or a vinyl ester resin. A prepreg containing carbon fiber coated with 3 to 10% by mass of a sizing agent having a mass average molecular weight of 1000 to 10000 on carbon fiber that has been opened in advance and a curable resin is clamped in a predetermined mold. A fiber-reinforced composite material, wherein the carbon fiber is separated and cured by the flow of the curable resin during clamping .